The present invention relates to X-ray analysis, and more specifically to the determination of properties of food or feed, such as the fat content of meat.
X-ray analysis for determining the fat content of meat has been known for several years. Such examples are described in numerous documents. U.S. Pat. No. 4,168,431 (Henriksen) discloses a multiple-level X-ray analysis for determining fat percentage. The apparatus includes at least three X-ray beams at different energy levels. DK PS 172 377 B1 discloses detection means for X-rays as well as a system for determination of properties of an item by use of X-rays. The system operates at a single energy level and applies two detection means separated by a X-ray attenuating material.
WO 92/05703 discloses a method and device for cutting food products. The positioning of suitable cuts are guided by use of X-ray scanning showing the distribution of tissue type in the product. U.S. Pat. No. 5,585,603 discloses a method and system for weighing objects using X-rays. A continuous X-ray analysis for a meat blending system is known from U.S. Pat. No. 4,171,164 (Groves et al).
The percentages of fat in two meat streams are determined by passing a beam of polychromatic X-rays through the streams, measuring both the incident and the attenuated beams. U.S. Pat. No. 4,504,963 discloses an apparatus, system and method for determining the percentage of fat in a meat sample through use of X-ray radiation techniques. An automatic calibration is obtained by use of three incident beams, all at same energy level. Validation of body composition by dual energy X-ray absorptiometry is described in Clinical Physiology (1991) 11, 331-341. (J. Haarbo, A. Gotfredsen, C. Hassager and C. Christiansen). Further studies on bodies are reported in Am. J. Clinical Nutrition 1993: 57:605-608. (Ole Lander Svendsen, Jens Haarbo, Christian Hassager, and Claus Christiansen).
Recently analysis of meat has been reported in Meat Science Vol. 47, No 1/2, 115-124, 1997 (A. D. Mitchell, M. B. Solomon and T. S. Rumsey). A thorough study on pork carcasses by use of dual-energy X-ray absorptiometry was reported by P Elowsson et al (1998) J. Nutr. 128 1543-1549 An Evaluation of Dual-Energy X-Ray Absorptiometry and Underwater Weighing to estimate Body Composition by means of carcass Analysis in Piglets. (p. 1543, l.andr. col.; p. 1544, l.col.; p. 1547, l. col.). Another analysis on pork carcasses is reported by Mitchell et al., J. Anim. Sci. (1998), vol. 76, pp 2104-2113. However, on page 2113 of this analysis it is specifically concluded that the X-ray analysis is too slow for compatibility with on-line processing. None of the above-mentioned prior art has so far lead to an efficient apparatus fulfilling the needs in a slaughterhouse. Generally the prior art shows difficulties when measuring layers of varying thickness, specifically thin layers adjacent to thick layers. Further the prior art is unable to measure and provide results as fast as required to be useful for online processing.
The presently applied apparatus in most slaughterhouses is a Continuous Fat Analyser (Wolfking A/S, Denmark) and Infratec 1265 (Foss Tecator AB, Sweden) using NIR technology. Also applied is Anyl-Ray (The Kartridg Pak Co., Iowa) using a single energy X-ray on a sample of well-defined weight or volume.
It is an object of the present invention to provide a method and apparatus enabling a faster and more accurate determination than hitherto known, of the fat content in a food or feed product, such as a batch of meat trimmings, allowing creation of specific products (such as sausages or minced meat) having a desired content of fat, which is much more accurate than presently possible.
The present invention also applies regression analysis and multivariate calibration. Such analysis is known from e.g. the applicant""s own WO 95/16201 disclosing the Determination of extraneous water in milk samples using regression analysis and multivariate calibration. Further, the applicant""s WO 98/43070 discloses Measurement of acetone in milk using IR spectroscopy and multivariate calibration. U.S. Pat. No. 5,459,677 discloses a calibration transfer for analytical instruments. The applicant""s WO 93/06460 discloses an infrared attenuation measuring system, including data processing based on multivariate calibration techniques, and the applicant""s U.S. Pat. No. 5,252,829 discloses a determination of urea in milk with improved accuracy using at least part of an infrared spectrum.
The present invention relates to a method of determining properties a medium of food or feed, such as the fat content of meat, by use of dual X-ray absorptiometry, the medium being a raw material of food or feed, a product or intermediary product of food or feed, or a batch, sample or section of the same, the method comprisingxe2x80x94scanning substantially all of the medium by X-ray beams having at least two energy levels, including a low level and a high level,xe2x80x94detecting the X-ray beams having passed through the medium for a plurality of areas (pixels) of the medium,xe2x80x94for each area calculating a value, Alow, representing the absorbance in the area of the medium at the low energy level,xe2x80x94for each area calculating a value, Ahigh representing the absorbance in the area of the medium at the high energy level, characterised by for each area generating a plurality of values being products of the type Alown*Ahighm wherein n and m are positive and/or negative integers or zero, and predicting the properties of the medium in this area by applying a calibration model to the plurality of values, wherein the calibration model defines relations between the plurality of values and properties of the medium.
The advantage over the prior art is a more accurate determination of the properties, such as the fat content in the medium. The accuracy is specifically improved over the prior art when measuring layers of varying thickness. A further advantage is due to the fact that using the method according to the invention almost the whole product is measured instead of a sampling. Generally, when using sampling in an inhomogeneous medium the extraction of a sample will introduce an error, because the sample may not be representative.
Preferably the plurality of values includes values Alown1/Ahighm1, wherein n1 and m1 are positive integers. Further on it is preferred that the plurality of values includes the values Alow, Ahigh, Alow2, Ahigh2, and Alow/Ahigh and/or at least one of the values Alow*Ahigh; Alow2*Ahigh; Alow*Ahigh2 and/or at least one of the values Alow*Ahigh; Alow2*Ahigh; Alow*Ahigh2; Alow*Ahigh4 and Alow2*Ahigh4 and/or at least one of the values Alow2/Ahigh; Alow/Ahigh2 and Alow2/Ahigh2; Alow3/Ahigh2; Alow4/Ahigh 2; 1/Ahigh4; Alow4/Ahigh3 ; Alow3/Ahigh4 and Alow4/Ahigh4.
Practical experiments have proved that such values contribute considerably to improve the accuracy.
Preferably the calibration model is obtained by use of a regression method being included in the group comprising Principal Component Regression (PCR), Multiple Linear Regression (MLR), Partial Least Squares (PLS) regression, and Artificial Neural Networks (ANN).
The present invention further relates to an apparatus for the determination of properties of a medium, such as the content of a component in the medium, the medium comprising a raw material of food or feed, a product or intermediary product of food or feed, or a batch, sample or section of the same, the apparatus comprising means (12, 14) for emitting at least two X-ray beams (16, 18) at two different energy levels, means for directing the at least two X-ray beams towards and through the medium, X-ray detection means (22, 24) covering a plurality of areas for detecting the two beams (16, 18) after passing through the medium, means (27, 28, 34, 35) for transferring and converting output signals from the detection means (22, 24) into digital data set for input to data processing means (38) for receiving, storing and processing the at least two data set representing X-ray images at the at least two different energy levels, the apparatus further comprising means for synchronising the at least two data sets and the data processing means including means for calculating values representing the absorbances (Alow, Ahigh) in each area of the medium at the at least two energy levels, characterised in that the data processing means comprise means for generating a plurality of values being products of the type Alown*Ahighm wherein n and m are positive and/or negative integers or zero, and means for predicting the properties of the medium in this area by applying a calibration model to the plurality of values, wherein the calibration model defines relations between the plurality of values and properties of the medium.
The advantage over the prior art is a faster and more accurate determination, which is so fast that it can be applied continuously on a process line in a slaughterhouse. The medium is arranged on a conveyor moving at substantially constant speed, and the at least two X-ray beams are fan-shaped, and the low level beam is detected by a first linear array, being dedicated to the detection of the low energy beam, and the high level beam is detected by a second linear array being dedicated to the detection of the high energy beam, each comprising a plurality of pixels.
The apparatus may be characterised by comprising at least one low energy X-ray source (12) arranged above the medium (20) for providing a fan-shaped low energy beam (16) substantially covering the width of medium and at least one high energy X-ray source (14) arranged above the medium (20) for providing a fan-shaped low energy beam (16) covering the width of medium (20) and a first X-ray detection means (22) arranged to be exposed to the fan-shaped low energy beam (16) and below the medium (20) a second X-ray detection means (24) arranged to be exposed to the fan-shaped high energy beam (18) and below the medium (20), and electronic means (34, 38, 42) including the data processing means (38) and communicating with the detectors (22, 24) and arranged to store and process data representing signals from the detection means (22, 24), and further comprising means (10) for moving the medium (20) relative to the X-ray beams (16, 18) or visa versa.
The apparatus may be characterised in that the data processing means include and/or communicate with means including data storage means comprising a calibration model prepared by use of multivariate calibration methods such as Artificial Neural Networks (ANN), or PCR, MLR or PLS regression analysis.
The apparatus may be characterised by comprising at least two sources (12, 14) emitting X-rays of two different energy levels.
The apparatus may be characterised by the two energy levels comprising a low energy level in a range between 35 and 75 keV, preferably between 45 and 70 key and most preferred about 62 key, and a high energy level in a range between about 60 and 140 keV, preferably between 80 and 130 key and most preferred about 120 keV.
The apparatus may be characterised by comprising filter means located in each of the beams (16, 18)
The apparatus may be characterised by comprising one X-ray source and two filter means splitting the beam into two beams of X-rays at two different energy levels.
The apparatus may be characterised in that the means (12, 14) for emitting at least two X-ray beams, the means for directing the at least two X-ray beams and the X-ray detection means (22, 24) are mutually fixed.
The apparatus may be characterised by comprising means (12, 14) for emitting spatially separated fan-shaped beams (16, 18).
The apparatus may be characterised in that the detection means (22,24) are covered by a scintillating layer, e.g. cadmium telluride, mercury iodide, and/or gadolinium oxysulphide.
The apparatus may be characterised by comprising conveyor means (10) arranged to carry container means (20), such as a tray or an open box, adapted to accommodate a random number of meat lumps of various sizes to be analysed, the conveyor means being arranged to let the container means (20) pass the at least two fan-shaped X-ray beams (16, 18).
The apparatus may be characterised by comprising conveyor means (10) wherein the conveyor belt is made from a material showing a low absorption of X-rays, and/or is split into two separate, spaced parts, the detector means (22, 24) being arranged in an open space between the two parts.
The apparatus may be characterised by comprising conveyor means (10) adapted to accommodate a Continuous flow of meat lumps of various sizes to be analysed, the conveyor means being arranged to let the meat lumps pass the at least two fan-shaped X-ray beams (16, 18).
The apparatus may be characterised by being arranged to perform the following steps: scan at least a section of a medium by X-ray beams having at least two energy levels, store data representing at least two X ray images of the medium, calculate the fat content and/or areal density for all points (pixels) obtained from the scanning by use of multivariate calibration models generated in a previously performed calibration step, multiply the fat content and areal density at each point, in order to generate a xe2x80x9cfat mapxe2x80x9d (in g/cm2) of the sample, add all points in the xe2x80x9cfat mapxe2x80x9d to give the total fat weight (Ftotal) of the sample, add all areal densities for the sample to give the total weight (Wtotal) of the sample, calculate the average fat content of the sample as the ratio Ftotal/Wtotal.
The present invention further relates to a method for calibration of an apparatus comprising preparation of a plurality of calibration samples consisting of specified food or feed products, such as minced pork meat, of various well-defined heights and properties, measuring the plurality of calibration samples in the apparatus, thereby obtaining data representing two X-ray responses of each sample, each response comprising a plurality of pixels, and wherein the data of each pixel, or the mean of a number of neighbouring pixels, are processed using the formulas:             A      low        =          -                        log          10                ⁡                  [                                                                      I                  sample                                ⁡                                  (                  low                  )                                            -                                                I                  dark                                ⁡                                  (                  low                  )                                                                                                      I                  air                                ⁡                                  (                  low                  )                                            -                                                I                  dark                                ⁡                                  (                  low                  )                                                              ]                                A      high        =          -                        log          10                ⁡                  [                                                                      I                  sample                                ⁡                                  (                  high                  )                                            -                                                I                  dark                                ⁡                                  (                  high                  )                                                                                                      I                  air                                ⁡                                  (                  high                  )                                            -                                                I                  dark                                ⁡                                  (                  high                  )                                                              ]                    
or similar expressions for calculation of values representing the absorbance in an area of the medium above a pixel or a number of neighbouring pixels,
generating a plurality of values of the type Alown*Ahighm,, wherein n and m are positive and/or negative integers and/or zero, correlatingxe2x80x94by use of multivariate calibration methods, such as Artificial Neural Networks (ANN), or PCR, MLR or PLS regressionxe2x80x94the data set for all/or a plurality of calibration samples to the properties determined by other means, such as a reference method,xe2x80x94in order to determine a number of calibration coefficients, providing a calibration model comprising the number of determined calibration coefficients.
All calibration samples are prepared in such a manner that they are homogeneous and of fixed areal densities, and further by averaging each of the values over all pixels at least in a defined portion of the images.
The invention further relates to a method of predicting the fat content of meat, comprising use of a calibration model obtained by a method. The invention also relates to an apparatus comprising a calibration model determined by a particular method.
By use of the present invention it is possiblexe2x80x94more accurate and more rapidly than hitherto knownxe2x80x94to determine the fat content of a random number of meat lumps (such as trimmings or cuts) of various sizes in a container (or similar means for enclosing or carrying a load of meat) or directly on a conveyor belt. The measurement may be performed within a fairly short time, such as a few seconds, e.g. about 4.5 or 9 seconds per container, each container having a volume of e.g. about 0.1 m3. Preferably, a smaller volume, about e.g. 25 kg meat, is arranged in each container. Accordingly, the method and apparatus may be applied for on-line control of the production of various meat products, such as minced meat, and more specifically where minced meat is produced from meat trimmings of various sizes.
According to the applicant""s best knowledge multivariate calibration techniques have never been applied to X-ray analysis of meat, nor to X-ray analysis in general. The use of multivariate techniques solves a specific problem present when using the techniques according to the prior art. The known apparatus becomes highly inaccurate when measuring on a combination of thin and thick layers. When measuring meat lumps of various sizes the thickness of the layers through which the X-ray has to pass will vary considerably from 0 or almost 0 to a specified maximum. The use of a plurality of values allows a better accuracy of such measurements than hitherto known.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.